Gas assist system for recoil actuated firearms



E. M. HARVEY 3,110,222

GAS ASSIST SYSTEM FOR RECOIL ACTUATED FIREARMS Nov. l2, 1963 3Sheets-Sheet 1 Filed April 5, 1962 INI/NTOR.- Emi E M I-Iurvlgy E. M.HARVEY Nov. 12, 1963 GAS ASSIST SYSTEM FOR RECOIL ACTUATED FIREARMSFiled April 5, 1962 3 Sheets-Sheet 2 1N VEN TOR. Earle M Hurv ey 74,@momma SEL/M2 Nov. 12, 1963 E. M. HARVEY 3,110,222

GAS ASSIST SYSTEM FOR RECOIL ACTUATED FIREARMS Filed April 5, 1962 5Sheets-Sheet 5 INVENTOR. T Emi@ M Hmvv En BY I 8 j fsmaQ/mf Unite States3,110,222 GAS ASSIST SYSTEM FR RECEL ACTUATEED FIREARMS Earle M. Harvey,Agawam, Mass., assigner to the United States of America as representedby the Secretary of the Army Filed Apr. 5, 1962, Ser. N 185,@86 2claims. (ci. s9-rs9) (Granted under Title 35, US. Code (1952), sec. 266)in the barrel by discharge of the cartridges is oftentimes insufficientto energize the guns operating mechanism. Therefore, an .assist must beprovided by adding a booster which utilizes gas pressure to impartadditional energy to the banrel.

These boosters are conventionally mounted on the front end of a barreljacket which is ixed to the gun receiver so as to inclose the barrel.The discharge gases are partially intercepted by an `annular pocket inthe booster so as to act rearwardly against the front end of the barrelto supplement the recoil energy transferred thereto. These boosters,which require the support of a barrel jacket, make it difficult andgenerally impossible to mount a front sight and other accessories on themuzzle of the gun. Moreover, these Aboosters have a tendency to befouled by copper and carbon build-up to the extent that the barrel isblocked against reciprocation.

In the application for a Machine Gun Seleotively Operated by a Gas orRecoil System, Serial No. 185,485, filed April 5, 1962 by lohn L.Lochhead, there is taught a machine gun which is selectively operated byeither a gas system or a recoil system. However', when the cartridgesutilized by su-ch gun are of low-energy types, the recoil force impartedto the barrel is insutcient to operate the gun. Consequently, gas assistmust be provided. The conventional igas booster is not practical withthis gun, which is adaptable for hand tiring, because a barrel jacketwould add to the weight and the bulk of the weapon and would intenferewith the mount-ing of a iirst sight and other accessories on the muzzleend of the banrel.

It is, therefore, one object of this invention to provide for suchrecoil-operated guns a gas assist device which will not interfere withthe installation of a sight or other accessory on the -front end of thegun barrel.

lt is another object of this invention to provide such a gas assistdevice which will bleed gases from the gun barrel midway along thelength thereof where the gases are the hottest to reduce considerablyany build-up of copper and carbon deposits.

It is a further Iobject of this invention to enlarge the scope of theaforementioned machine gun by adapting it for use with cartridges whichare of low-energy types.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawings in which:

FIG. 1 is a partially cross-sectioned side view of the rear portion ofthe machine gun with the bolt in battery position;

FIG. la is a forward continuation of FIG. 1 and shows the selecto-rindexed in position for operation of the machine gun by gas means;

FIG. 2 is an elevational View of the front portion of the receivershowing the selector indexed lfor gas operation of the machine gun andthe barrel in the battery position;

FIG. 3 is a longitudinally cross-sectioned View of the rear portion ofthe machine gun and shows the bolt in recoil position;

lFIG. 4 is a view taken along line 4 4 of FIG. 2;

FIG. 5 is a view taken along line 5 5 of FIG. 4;

FIG. 6 is a view taken along line 6 6 of FIG. 4;

FIG. 7 is a forward extens-ion of FIG. 3 and shows the selector indexedin position for operation of the machine gun by gas assist recoil means;

FIG. 8 is a view similar to HG. 2 but showing the selector indexed forgas assist recoil operation of the machine gun and the barrel in thedriving position;

FIG. 9 is a view taken along line 9-9 of FIG. 8;

FIG. 1'0 is a view taken along line litt-110 of FIG. 9;

FIG. 1l is a View taken along line 11 1.1 of FIG. 9; and

FlG. 12 is an exploded perspective view of the selector.

Shown in the iigures is a machine gun 1,2r which is selectively operableby gas pressure or recoil forces such as is disclosed in the applicationfor a Machine Gun Selectively Operated by a Gas or Recoil System, SerialNo. 185,485, led April 5, 1962 by lohn L. L'ochhead. Machine gun 12, isadapted for automatically firing a small caliber cartridge 14 which isof 7.62 caliber, or the like, and includes a receiver 16 in which a boltassembly 18 is mounted for sliding reciprocation between a forwardlocked position and a rearward recoil position. A barrel assembly 20' isjournalled in the front end of receiver 16 for longitudinalreciprocation between a forward battery position and a rearward drivingposition.

Barrel assembly 2li includes a barrel 22, the front portion of whichextends forwardly `from receiver `16, and a gas cylinder assembly 2,4which includes a gas cylinder 26 and a cooperating piston 2.8. Gascylinder 25 includes a central body portion 29 which is bracketed tobarrel Z2 approximately midway the length thereof so that the gasIcylinder is located within receiver 16. A cylindrical hole 3@ extendslaterally thnough body portion 2,9 and communication is provided betweensuoh hole and bore 31 of barrel 22 by a vertical passageway 32. Piston2S is slidingly mounted in a bore 34 which extends forwardly in gascylinder 26 from the rear end thereorf to an end wall '36 locatedrearwardly of hole 30. A gas port dit extends forwardly from end wall316 so as to provide communication between bore 34 and hole Sil.

Extending integrally .forward from body portion 29 is a cylindricalpiston portion i2 which is smoothly machined around the outside. Aconcentric bore 44 extends forwardly through piston portion i2 from hole3i? and such piston pontion is received by a mating chamber 46 in acylinder block 4S. which is fixed to receiver 16. A close sliding lit isprovided between piston portion 4.2, and the wall of chamber 46 so as`to eliminate as much as possible gas leakage thereby. Lf necessary, gasseal rings can be installed on piston portion 4t2.

A selector Sil is rotatingly received by a hole 3ft so as to beselectively indexed in a Gas position or a Recoil position. Selector Silincludes a cylindrical rod 52 received yby hole 3d and such rod extendsfrom opposite sides of body portion 29 to form an extending end 54 onthe left side of gas cylinder 26 and another extending end 56 on theright side thereof. Provided in rod 52 is a first aperture 58 and asecond aperture `60 which are radially disposed apart so as to convergeat the center of the rod. When selector 5d is indexed in the Gasposition, first aperture 53 is in registry with gas port 40 and secondaperture 6d is in registry with passageway 32 so that discharge gasesare directed from bore 31 of lbarrel 22 to bore 34 to act upon piston2S. When selector 50 is indexed in Recoil position by 90 rotation of theselector in a clockwise direction, looking towards the right side ofmachine gun 12 and as shown in FIG. la, first aperture 58 is in registrywith passageway 32 and second aperture 6!` is in registry with bore 44so that discharge gases are directed from bore 3d of barrel Z2 intochamber 46.

Extending end 54 on the left side of selector 50 is slabbed off atdiametrically opposed sections to form an ear 62 which is symmetrical tothe lateral plane which is coincident with the main axis of firstaperture 58. When selector 56 is indexed in the Recoil position so thatthe longest axis of ear 62 is longitudinally disposed, the ear isreceivable by a mating longitudinally disposed channel 64 in receiver f6and is slidable along the channel during reciprocation of barrelassembly 20 `to and from the driving position. Channel 64- has a widthsimilar to the short axis of ear 62 and is interrupted by an oval recess66 which is located so as to be in registry with selector Stl whenbarrel assembly 26 is in the forward battery position. Recess 66 has aradius similar to that of rod 52 so that the selector is free to berotated between the Gas and Recoil positions when barrel assembly Ztl isin battery position.

Extending end 56 on the right end of selector 50` extends throughreceiver 16 and provided on such extending end is a button 68 whichprovides means `for manually rotating the selector. Extending end S6 isinterrupted by a pair of diametrically opposed segmental cuts 7Gl whichform a key section '/"2 which is coincidental with the same lateralplane as ear 62. Key section 72 is slidingly receivable by a slot '74 inthe right side of receiver 16 to permit reciprocation of barrel assembly2d when the long axis of the key section is in alignment with such slot.The width of slot '74 is similar to the short axis of key section '72and such slot is interrupted -by a circular orifice 76 which is arrangedto be in registry with selector 5G when barrel assembly 26 is in batteryposition and which has a radius similar to that of rod 52. Thus, whenselector t) is in Recoil position, key section 72 is in alignment withslot 74 and ear 62 is in alignment with channel 64 so that barrelassembly 20 is free to reciprocate between the battery and drivingpositions. When selector 5G is rotated to the Gas position so that thelong axes of ear 62 and key section 72 are vertically disposed, barrelassembly is blocked in battery position because of the cooperation ofthe ear with the walls of recess 66 and of the key section with the wallof orice 76.

As disclosed in the aforementioned patent application, bolt assembly 18includes a carrier Sil, a bolt 82, which is mounted thereon for relativerotational and longitudinal displacement, and cam means 84 operationallydisposed between the carrier and bolt for converting relativelongitudinal displacement of the -bolt and carrier to rotationaldisplacement of the bolt so that the lbolt is locked to the barrelduring forward displacement of the carrier relative to the bolt and isunlocked during rearward displacement of the carrier relative to thebolt. An accelerator 86 is pivotally mounted in receiver 16 and isarranged according to conventional design to accelerate bolt assembly 13to the rearward recoil position when barrel assembly is adjacent itsdriving position. A driving rod 8S extends forwardly from carrier 80 soas to be contactable by piston 28 to transfer the energy applied theretoby gases bled from the bore of barrel 22 to the carrier.

Thus, when machine gun 12 is to be operated by gas means, selector 50 isindexed in the Gas position, which is identifiable by the marking of Gason the right side of receiver 16 and an arrow on button 68. Withselector 5t) in the Gas position, ear 62 and key section 72 arepositioned in recess 66 and orifice 76, respectively, to blockdisplacement of barrel assembly 2t)y `from battery position and firstaperture 58 is in registry with `gas port 40 and second aperture 66 isin registry with passageway 4 32 so that discharge gases aretransferable from the bore of barrel 22 into bore 3d to act againstpiston 28.

iVhen machine gun l2 is to be operated by recoil energy in barrelassembly 20, selector S0 is indexed in the Recoil position which isidentifiable by the marking of Recoil on the side of receiver 16 and anarrow on button 63. With selector Sti in the Recoil position, ear 62 andkey section 72 are respectively aligned with channel 64 and slot '74 soas to be receivable thereby and, consequently, barrel 2t) is free toreciprocate to and from driving position. Also, first aperture 58 is inregistry with passageway 32 and second aperture 6d` is in registry withbore 44 so that, when cartridge M- is discharged in barrel 22, barrelassembly 20 is energized by the recoil forces and, when the projectileof the cartridge passes passageway 32, gases are bled from the bore ofthe barrel through bore 4d into chamber 46. The gases received bychamber 46 add to the recoil energy in barrel assembly 2t? so thatsuicient energy is imparted thereto to drive bolt assembly 1S to therecoil position and perform its operating functions.

From the foregoing it is clearly apparent that there is provided hereinfor recoil operated firearms a gas assist system which is ideally suitedto those firearms which are hand fired as the device adds little weightand bulk to the firearms and the muzzle end of the barrel is free forthe mounting of accessories thereon. Moreover, the gas assist system isan improvement over conventional booster devices as it is notsubjectable to copper and carbon buildup.

Although a particular embodiment of the invention has been described indetail herein, it is evident that many variations may be devised withinthe spirit and scope thereof and the following claims are intended toinclude such variations.

I claim:

l. A machine gun including a receiver, a barrel journaled in saidreceiver so as to be movingly responsive to recoil energy produced insaid barrel by discharge of a cartridge therein, a bolt assembly mountedin said receiver for reciprocation therein, accelerator means fortransferring energy from said barrel to said bolt assembly forreciprocation thereof, a gas cylinder ixedly mounted on said barrel, apassageway arranged between said gas cylinder and said barrel forbleeding gases therefrom into said gas cylinder, and means disposed incooperation with said gas cylinder for selectively blocking said barrelagainst displacement and utilizing the gases bled from said barrel toenergize said bolt assembly for reciprocation and for selectivelyreleasing said barrel for reciprocation and utilizing the gases bledfrom said barrel for supplementing the recoil energy in said barrel toprovide suflicient energy in said barrel for reciprocating said boltassembly when transferred thereto by said accelerator means.

2. A machine gun including a receiver, a bored barrel journaled in saidreceiver so as to be movingly responsive to recoil energy produced insaid barrel by discharge of a cartridge therein, a bolt assembly mountedin said receiver for reciprocation therein, accelerator means mounted insaid receiver so as to transfer energy from said barrel to said boltassembly for reciprocation thereof, a gas cylinder fixedly mounted onsaid barrel, a passageway arranged between said gas cylinder and saidbarrel for bleeding gases therefrom into said gas cylinder, a bore insaid gas cylinder, a piston slidingly mounted in said bore and arrangedto be actuatable against said bolt assembly by gases received by saidbore, a hollow piston portion on said gas cylinder, a cylinder blockfixed to said receiver and provided with a chamber for slidinglyreceiving said piston portion, a hole extending laterally through saidgas cylinder, conduit means extending between said hole and the insideof said barrel, between said hole and said bore in said gas cylinder andbetween said hole and the inside of said piston portion, a selectormounted in said hole for rotation between a iirst position 5 6 and asecond position, aperture means arranged in said when said selector isin the rst position and for releasselector completing communicationbetween said barrel ing said barrel for displacement when said selectoris in and said bore in said gas cylinder for passage of gases the secondposition. thereinto when said selector is in said rst position and forcompleting communication between said barrel and 5 References Cited inthe file 0f this patent the inside of said piston portion when saidselector is in UNITED STATES PATENTS the second position, andcooperating means in said selector

1. A MACHINE GUN INCLUDING A RECEIVER, A BARREL JOURNALED IN SAIDRECEIVER SO AS TO BE MOVINGLY RESPONSIVE TO RECOIL ENERGY PRODUCED INSAID BARREL BY DISCHARGE OF A CARTRIDGE THEREIN, A BOLT ASSEMBLY MOUNTEDIN SAID RECEIVER FOR RECIPROCATION THEREIN, ACCELERATOR MEANS FORTRANSFERRING ENERGY FROM SAID BARREL TO SAID BOLT ASSEMBLY FORRECIPROCATION THEREOF, A GAS CYLINDER FIXEDLY MOUNTED ON SAID BARREL, APASSAGEWAY ARRANGED BETWEEN SAID GAS CYLINDER AND SAID BARREL FORBLEEDING GASES THEREFROM INTO SAID GAS CYLINDER, AND MEANS DISPOSED INCOOPERATION WITH SAID GAS CYLINDER FOR SELECTIVELY BLOCKING SAID BARRELAGAINST DISPLACEMENT AND UTILIZING THE GASES BLED FROM SAID BARREL TOENERGIZE SAID BOLT ASSEMBLY FOR RECIPROCATION AND FOR SELECTIVELYRELEASING SAID BARREL FOR RECIPROCATION AND UTILIZING THE GASES BLEDFROM SAID BARREL FOR SUPPLEMENTING THE RECOIL ENERGY IN SAID BARREL TOPROVIDE SUFFICIENT ENERGY IN SAID BARREL FOR RECIPROCATING SAID BOLTASSEMBLY WHEN TRANSFERRED THERETO BY SAID ACCELERATOR MEANS.